Ultrahigh-frequency generator



Sept. 22, 1953 s. RAMO ULTRAHIGH-FR* EQUENCY GEIEERATGR Filed March 15,1945 Inventor:

Flam o, 5.1% tomey Slmon b 17%? y His 0 Patented Sept. 22, 1953ULTBAHIGH-FREQUENCY GENERATOR Simon Ramo, Schenectady, N. Y., assignorto General Electric Company, a corporation of New York Application March15, 1945, Serial No. 582,917

'1 Claims. (Cl. 315-) My present invention relates to ultra highfrequency systems and it has for its primary object the provision of anew and improved'generator of waves of extremely short length.

In the design and construction of oscillators for generating waves ofextremely short length of the order of one or two millimeters,difliculties have been encountered because of the progressivedeterioration of the usual methods of using electrons to produceamplification, both because of the short transit times of the electronsand of the very large ohmic losses in the circuits. An even moreimportant limitation is the difficulty of bringing the'resonatingstructure of the generator in close proximity with a suflicient numberof electrons. Essentially,v the resonators employed in such generatorsare closed chambers with holes or apertures which permit electrons topass therethrough. The amount of current required for the excitation ofsuch resonators when one attempts generation of waves having a wavelength of the order of one millimeter is too great for the relativelysmall region through which this current is permitted to pass. Thus, forexample, the current required for the generation of wave lengths of onemillimeter is approximately the same as that required for the generationof wave lengths of one centimeter. However, when a resonant structure ofthe usual type is reduced to the size required for the one millimeterwave there is not sufiicient space available for passage of a current ofthe magnitude required to excite the resonator.

It is another object o1 my invention to provide a new and improved ultrahigh frequency resonant circuit for use in the generation of extremelyshort wave lengths.

It is a further object of my invention to provide a new and improvedultra high frequency electron discharge device.

It is still another object of my invention to provide a new and improvedultra high frequency generator of the reflex oscillator type.

It is a still further object of my invention to provide a new andimproved ultra high frequency resonant circuit adapted to be enclosed inan electric discharge device and having multiple circuits for generatinglarge amounts of short wave energy.

It is still another object of my invention'to provide a new and improvedultra high frequency device for generating waves of extremely short wavelength and in which the generation of longer waves is prevented.

It is a still further'object of my invention to provide a new andimproved grid structure for an ultra high frequency electron dischargedevice.

Briefly stated, my invention consists in the employment in an ultra highfrequency generator of the reflex oscillator type of a porous resonatingstructure which can be substantially saturated with the-electrons and inwhich the resonant structures are formed from very thin wires, the wiresbeing constructed in a network so that the resonant system is multiplein character, the resonator being divided into a large number of shortwave length cells by the network of fine wires.

For a better understanding of my invention,

reference may be had to the following description taken in connectionwith the accompanyand side views, respectively, of a single resonator ofthe multiple resonator of Fig. 2; and Fig. 5 is a schematic illustrationof an ultra high frequency system employing the short wave generator ofFig. 1.

In the portion of the electrode structure of a high frequency generatorillustrated in Fig. 1, there is shown a source of electrons in the formof a cathode I having a flat disk emitting surface and heated by asuitable filament 2. Electrons emitted by the cathode Iare focused by afocusing electrode in the form of a grid 3 supplied with suitablenegative potentials with respect to the cathode I. The focused electronsare directed toward a reflector collector electrode 4 and, in theirpassage toward the reflector 4, pass through a multiple resonatorstructure comprising two layers 5 and 6 of fine parallel wires separatedby a layer I of transverse wires. The electrode elements described aboveare enclosed in an envelope indicated schematically by the numeral 1a.

The construction of the grid resonator 5-4 may best be understood byreference to the perspective view of Fig. 2. The fine parallel wires 5and 6 form the bottom and top layers, respectively, of a nearlyrectangular cross section wave guide resonator, while the transversewires I form the sides of such a guide. The wires I like:-

wise function to short-circuit the parallel wires,

aosas're 3 I; 6 at the point of intersection.- The spacing between theparallel transverse wires 1' is made equal to a multiple of a half wavelength at the desired operating frequency of the oscillator.

Figs. 3 and 4 show the vertical and side views, respectively, of asingle half wave length open wire line resonator of the multipleresonator structure of Fig. 2. As is indicated, the electron stream 8from the cathode i of the discharge device passes on both sides of theindividual half wave length open lines. Since the wires 5, 6 are spacedrelatively close together, the electrons of the stream have 'a moreeflective coupling with the individual resonators of the multipleresonator structure, the space in each of the rectangular openings beingsubstantially completely saturated with electrons and substantiallyevery electron is actively coupled with the resonators, i. e., everyelectron has a direct influence or excitation effect on the resonators.Thus, in the complete tank circuit formed by the grid wires 5, 6, I,there is a greater volume of space available for the active spacecharge, thus allowing larger ultra high frequency currents of extremelyshort wave lengths to be generated.

The electric discharge device of Fig. 1 operates generally according tovelocity modulation principles, the electron beam from the cathode Ibeingivelocity modulated periodically so that successive groups ofelectrons are alternately accelerated and decelerated, tending to groupthe electrons in the component parts of the beam after these parts havetraversed the velocity modulation gaps. The particular form of electricdischarge device described operates in accordance with reflexprinciples. Thus, after undergoing velocity modulations, electrons aregiven an opportunity to assume a charge density distribution incident tothe effect of the velocity modulation and are reversed in the directionsof travel to reenter the short wave length cells of the cavityresonators, delivering energy to the electromagnetic fields thereof.

v In the device of Fig. 1, the electron beam is established by virtue ofthe unidirectional potential impressed between the resonator -1 and thecathode I from any suitable source of voltage, such as the battery 9.The electrons of the electron beam initially assume the velocitydetermined by the accelerating potential impressed upon the grid wires5'|. A negative potential I ments 1.

with respect to the cathode disk I is impressed on the focusing grid 3which tends to direct the electrons of the beam into component parts,illustrated by the arrows ill, which pass through the parallel gapsformed in the grid wires 5 and 6. As they pass through each of theserectangular openings in the grid structure 5-1, the electrons exciteeach of the individual resonators toset them into oscillation andestablish across the gaps between the wires 5, 6 an alternating ultrahigh frequency potential incident to the electromagnetic field whichexists within each of the individual resonators. By virtue of thealternating nature of this potential, electrons, which are in the regionbetween the planes of wires 5, 5 during periods of time when the wire 5is positive with respect to the wire 6, will undergo an acceleration.Consequently, the electrons, after traversing the grid structure,proceed into the region of the field produced by the retarding reflectorcollector electrode 4. The potential of the electrode 4, furthermore,may be negative with respect to the cathode, as well as being negativeto the resonator structure, such negative potential 4 being supplied byany suitable source of voltage, such as the battery II. The distancewhich the electrons proceed in their path beyond the grid 5 is afunction of the kinetic energy of each electron, this kinetic energybeing. determined by the voltage used to accelerate the electrons. Theelectrons are reversed by the potential of the electrode 4 to re-enterthe cavity resonator and deliver additional energy to the resonatoraccording to reflex oscillator principles.

One of the advantages of the resonator structure described above is thatthere is greater utilization of the volume of space between the cathodeI and the reflector electrode 4 for the active space charge, thuspermitting the generation of larger currents of extremely short wavelength. In the operation of the oscillator, the gap at which velocitymodulation takes place receives its high frequency voltage from each ofthe given individual resonator elements constituted by the portions ofgrid wires 5, 6 between the short-circuiting elements 1.

An additional advantage of the resonator structure illustrated is thefact that this particular arrangement eliminates the possibility ofgen-- erating oscillations at a wave length longer than the distancebetween the short-circuiting ele- The structure, therefore, isespecially suited for generation of waves of extremely short length,viz., of the order of a few millimeters. Moreover, in the multipleresonator structure, there is no problem of strapping or joining theindividual resonators, the wires 1 functioning both as such connectorsas well as short-circuits for lower frequencies. The grid structureitself is basically very simple and may be constructed by the windingofparallel wired grids.

In Fig. 5, there is illustrated schematically an ultra high frequencysystem which is particularly adapted for communication systems employingvery high frequencies, as well as radar imaging systems and systems formeteorological investigations. In this system, an electronic dischargedevice of the form shown in Fig. 1 and having an enclosing envelope 1!is placed at the focal point of a parabolical reflector l3 and theleakage by radiation from all of the multiple resonators of the gridstructure of the device is utilized to form a beam directed by thereflector i3.

While I have shown particular embodiments oi. my invention, it will ofcourse be understood that I do not wish to be limited thereto sincevarious modifications may be made, and I contemplate by the appendedclaims to cover any such modifications as fall within the true spiritand scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. An ultra high frequency oscillator comprising an electric dischargedevice having a cathode, a reflector electrode, and a resonant structurelocated between said electrodes, said structure comprising two layers ofparallel wires forming a plurality of parallel connected sections ofopen wire transmission lines, and transverse conductors disposed betweensaid layers at points spaced apart by a distance equal to an integernumber times a half wave length at the desired operating frequency ofsaid oscillator.

2. An ultra high frequency electron discharge device including electrodemeans for establishing an electron discharge and an electron perviousresonant electrode structure positioned in the path of said dischargeand comprising a plurality of spaced conducting loops each positioned ina plane parallel to the path of said discharge, said loops beingelectrically resonant at the desired operating frequency of said device.

3. An ultra high frequency electron discharge device including electrodemeans for establishing an electron discharge and an electron perviousresonant electrode structure positioned in the path of said dischargeand comprising a plurality of spaced rectangular conducting loops eachpositioned with its plane parallel to the path of said discharge, saidloops being electrically resonant at the desired operating frequency ofsaid device.

4. An ultra high frequency electron discharge device including a cathodeand an electrode for establishing an electron discharge in said device,and a resonant electrode structure in the path of said dischargecomprising a plurality of layers of spaced wires, each wire in eachlayer being in alignment with a corresponding wire in another layer, thewires in each said layer being spaced apart to permit the passage ofelectrons through said layer and being positioned transversely to thepath of electrons in said discharge, said wires forming multipleresonators electrically resonant at the operating frequency of saiddevice.

5. An ultra high frequency electron discharge device including a cathodeand an electrode for establishing an electron discharge in said device,and a resonant electrode structure in the path of said dischargecomprising a plurality of parallel layers of spaced parallel wires, eachwire in each layer being in alignment with a corresponding wire inanother layer, ,the wires in each said layer being spaced apart topermit the passage of electrons through said layer and being positionedtransversely to the path of electrons in said discharge, said wiresforming multiple resonators electrically resonant at the operatingfrequency of said device.

, 6. An ultra high frequency electron discharge device including meansfor establishing an electron discharge and a resonant electrodestructure positioned in the path of said discharge comprising aplurality of layers of spaced wires positioned transversely to the pathof said discharge, the wires in each said layer being spaced apart topermit the passage of electrons through said layer and being alignedwith corresponding wires in the other layer, and conductive meansdisposed between said layers shortcircuiting corresponding wires in eachof said layers at predetermined longitudinally spaced points thereof.

7. An ultra high frequency electron discharge device including means forestablishing an electron discharge and a resonant electrode structurepositioned in the path of said discharge comprising a plurality ofparallel layers of spaced parallel wires positioned transversely to thepath of said discharge, the wires in each said layer being spaced apartto permit the passage of electrons through said layer and being alignedwith corresponding wires in the other layer, and conductive meansdisposed between said layers shortcircuiting corresponding wires in eachof said layers at predetermined longitudinally spaced points thereof.

SIMON RAMO.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date Re. 22,580 Nouromtsefi et al. Dec. 19, 1944 1,353,976 StoekleSept. 28, 1920 1,465,381 Trimble Aug. 21, 1923 1,666,071 Perryman Apr.17, 1928 1,844,319 Hatt -l Feb. 9, 1932 2,043,659 Herriger June 9, 19362,087,252 Gumi July 20, 1937 2,105,924 Mendenhall Jan. 18, 19382,115,866 Lux May 3, 1938 2,205,475 Hollmann June 25, 1940 2,244,747Varian et a1 June 10, 1941 FOREIGN PATENTS Number Country Date 560,982GreatBritain May 1, 1944

